Wills, now an analyst at CNA in Arlington, Va., recently earned a Ph.D. in military history from Ohio University, as well as a Certificate in Contemporary History from the Contemporary History Institute.

In the piece, Wills explains the concept of “gray zone warfare,” which the U.S. Special Operations Command defines as “competitive interactions among and within state and non-state actors that fall between the traditional war and peace duality.” Most recently this tactic was used by Russia and China in their efforts to slice off territories in their immediate neighborhoods. Russia’s use of irregular soldiers known as “little green men” to occupy the Crimean peninsula as well as parts of Ukraine qualifies as this type of warfare. China’s push into contested islands in the South China Sea also qualifies. Wills points out that the use of gray zone warfare is not exclusive to the aforementioned powers, however, and that U.S. President Franklin D. Roosevelt actually used the strategy during World War II.